"I can assure you that we are outraged too. What puzzles me more is that T-Mobile did not speak with us before or after they launched this clearly inappropriate and ill-conceived marketing promotion," he wrote.

He also had a message for T-Mobile: "I would like to remind you that our long-standing partnership was once productive and profitable for both Blackberry and T-Mobile. I hope we can find a way forward that allows us to serve our shared customers once again."

T-Mobile confirmed that Blackberry devices were still available for people to buy and that other users of Blackberry devices could switch to the network if they wanted.

Blackberry was once a dominant player in the smartphone market but has lost ground to Apple, Samsung and other rivals.

It launched a new model, the Z10, in 2013 which it hoped would help revive its fortunes but disappointing sales and poor financial results led to a company shake-up.

Mr Chen was appointed interim chief executive in November and the company announced that 4,500 jobs, or 40% of its workforce would be cut.

On starting his role, Mr Chen said he would refocus the company to rely less on handsets and more on the company's services business.